Abstract: Systems and methods for detecting one or more physical communication link breaks are disclosed. An indication of a failure of one or more network layer links may be received. A physical layer link associated with the one or more network layer links may be determined based on the indication of the failure, and based on data indicating one or more associations between network layer links and physical layer links. A score may be determined indicating a probability that the physical layer link comprises a failure associated with a break in a physical communication link of the physical layer link based on determining a total quantity of the network layer links associated with the physical layer link, and based on a quantity of one or more network layer links associated with the indication of the failure.

Abstract: Query conditions are received in a cache from a query optimizer of a Database Management System (DBMS). Dynamic statistics for the query conditions are maintained in the cache. Actual statistics are received in the cache after the query conditions are executed in the DBMS. Entropy-based estimated selectivity values for executing the query conditions are provided to the query optimizer to develop a query plan for executing queries having the query conditions. The entropy-based estimated selectivity values based, at least in part, on the dynamic statistics and the actual statistics.

Abstract: Query conditions are received in a cache from a query optimizer of a Database Management System (DBMS). Dynamic statistics for the query conditions are maintained in the cache. Actual statistics are received in the cache after the query conditions are executed in the DBMS. Entropy-based estimated selectivity values for executing the query conditions are provided to the query optimizer to develop a query plan for executing queries having the query conditions. The entropy-based estimated selectivity values based, at least in part, on the dynamic statistics and the actual statistics.